Interpretation Of Microstructure Research Articles

The influence of alkali content on the electrical resistivity and transport properties of cementitious materials

This paper examines the role of alkali content on the transport properties of cementitious materials. While cement with high alkali content may be a concern due to the potential for alkali silica reaction (ASR), the alkali content also influences the electrical properties of pore solution and the bulk cementitious system. Higher concentrations of alkalis decrease the resistivity of the pore solution. However, the alkalis may also impact the microstructure formed during hydration. This paper examines the role of alkali content on both the pore solution and on the microstructure that forms. Water vapor desorption measurements indicate that systems with a higher alkali content have a lower overall porosity. This dense microstructure is not caused simply by a higher degree of hydration (DOH) (i.e., an increase in reacted products), as suggested by loss on ignition (LOI), but rather possibly from the improved morphology and distribution of calcium hydroxide, as observed with scanning electron microscope (SEM).These improvements in the microstructure alter the electrical resistivity and the results of steady and non-steady state migration tests. This indicates that with higher alkali content, cement may have a beneficial influence on reducing chloride ion transport. Furthermore, alkali leaching during saturated curing is observed, quantified, and discussed as it relates to the interpretation of electrical measurements and microstructure formed.

Microstructures of microgranitoid enclaves and the origin of S-type granitoids

Arguments about the origin of microgranitoid enclaves (‘mafic inclusions’) in S-type granitoids partly revolve around the interpretation of microstructures. Microstructural evidence indicates that the enclaves are of igneous origin, rather than the metamorphic or partly melted metamorphic origin favoured by some proponents of the restite unmixing hypothesis for granitoid formation. Microgranitoid enclaves in S-type granitoids have no bearing on the restite unmixing hypothesis, because they are globules of hybrid magma incorporated into the magma chamber after the formation of the host magma. Microstructural and isotopic evidence indicates mixing between felsic S-type and mantle-derived enclave-forming magmas in the general magmatic system. However, the extent to which magma mixing contributes to the chemical composition of S-type granitoids remains controversial.

Plausibility Tracking: A method to evaluate anatomical connectivity and microstructural properties along fiber pathways

Diffusion MRI is a non-invasive method that potentially gives insight into the brain's white matter structure regarding the pathway of connections and properties of the axons.Here, we propose a novel global tractography method named Plausibility Tracking that provides the most plausible pathway, modeled as a smooth spline curve, between two locations in the brain. Compared to other tractography methods, plausibility tracking combines the more complete connectivity pattern of probabilistic tractography with smooth tracks that are globally optimized using the fiber orientation density function and hence is relatively robust against local noise and error propagation. It has been tested on phantom and biological data and compared to other methods of tractography. Plausibility tracking provides reliable local directions all along the fiber pathways which makes it especially interesting for tract-based analysis in combination with direction dependent indices of diffusion MRI.In order to demonstrate this potential of plausibility tracking, we propose a framework for the assessment and comparison of diffusion derived tissue properties. This framework comprises atlas-guided parameterization of tract representation and advanced bundle-specific indices describing fiber density, fiber spread and white matter complexity. We explore the new method using real data and show that it allows for a more specific interpretation of the white matter's microstructure compared to rotationally invariant indices derived from the diffusion tensor.

Microfabric diversity and grain shape analysis of fault rocks from the selected areas of the Western Tatra Mountains

Fault rocks in brittle and brittle-ductile shear zones played a key role in the evolution of the Western Tatra Mountains crystalline rocks (Poland–Slovakia). Microfabrics of these rocks, including grain shape analyses, were investigated in the six areas of the Western Tatra Mountains. Based on studies of thin sections, 14 types of fault rock microfabric are distinguished, according to the following criteria: (a) the presence and abundance levels of a cataclastic matrix and (b) the presence and form of a preferred orientation features. General tendencies observed in these areas indicate southwards increasing non-coaxial deformation as well as the domination of ultracataclasites or ultramylonites to phyllonites in areas with negative relief (e.g., sedlo Zabrat’ Pass, Dziurawa Przełęcz Pass). A model of shear zone evolution embracing following three stages is proposed: (1) deformation partitioning and block-controlled cataclastic flow, (2) matrix-controlled cataclastic flow, (3) selective leaching and deposition of silica, leading to the formation of softened and hardened deformation domains respectively. These microstructural observations were supported by statistical analyses of the grain shape indicators (compactness, isometry, ellipticity, solidity, convexity). Two trends of relationships between compactness and convexity were noted: the first, horizontal on the correlation diagrams, was interpreted as an effect of rapid cataclasis and then sericitization, the second, with a strongly negative correlation coefficient, was considered as an effect of long-term cataclastic flow. The different microfabric data and microstructural interpretations described in this paper are consistent with a new model of the tectonic history of the Western Tatra Mountains evolution, with an important role for a non-coaxial deformation during Alpine orogeny in brittle and brittle-ductile conditions.

Mechanism and Kinetics of Solid-State Transformation in High-Temperature Processed Linepipe Steel

A relatively new class of linepipe steels with yield strength greater than 500 MPa created for thermomechanical processing at temperatures in excess of 1473 K (1200 °C) has established a firm foothold in the market for modern, large diameter, and high-pressure gas transmission systems. The design concept for the steels takes advantage of the enhanced role which higher levels of niobium can play in very low carbon steels, during the plate manufacturing process. The transformation products observed after cooling have been interpreted in conflicting ways in the literature, using ambiguous terms which are not established rigorously. Revealing characterization experiments have therefore been conducted to establish that the principal transformation product grows by a displacive transformation mechanism, and that it is properly identified as bainite. The implications of this, on both the interpretation of microstructure and on the processing of the steel, are discussed.

Synthesis of Mixed Ceramic MgxZn1–xO Nanofibers via Mg2+ Doping Using Sol–Gel Electrospinning

We report on the synthesis of tuned energy band gap Mg(x)Zn(1-x)O nanofibers (NFs) with different Mg(2+) content via the sol-gel electrospinning (ES) technique wherein the addition of the doping material affects not only the morphologies of as-spun ZnAc/PVA and MgAc/ZnAc/PVA nanofibers but also the crystal microstructure and optical properties of calcined ZnO and Mg(x)Zn(1-x)O nanofibers. Following an appropriate aqueous solution preparation of magnesium acetate (MgAc) and zinc acetate (ZnAc) with poly(vinyl alcohol) (PVA), electrospinning is performed and then as-spun nanofibers are calcined in an air atmosphere at 600 °C for 3 h. As-spun and calcined nanofiber diameters and morphologies are evaluated with scanning (SEM) and transmission (TEM) electron microscopies, whereas crystalline microstructural interpretations of ZnO and Mg(x)Zn(1-x)O are conducted with wide-angle X-ray diffraction spectra (XRD). Surface chemical composition and elemental evaluation of calcined nanofibers are examined with X-ray photoelectron spectroscopy (XPS), and optical properties and crystal defect analyses of the calcined nanofibers are conducted with photoluminescence spectra (PL). We observe a sharp reduction in fiber diameter upon calcination as a result of the removal of organic species from the fibers and conversion of ceramic precursors into ceramic nanofibers, and the appearance of a range of fiber morphologies from "bead in a string" to "sesame seed" coverage depending on fiber composition. Because Zn(2+) and Mg(2+) have similar ionicity and atomic radii, some Zn(2+) atoms are replaced by Mg(2+) atoms in the crystals, leading to a change in the properties of crystal lattices. The band gap energy of the calcined fibers increases significantly with addition of Mg(2+) along with an increase in the ultraviolet (UV) photoluminescence emission of the fibers.

Surface maturation scoring for oesophageal squamous intraepithelial neoplasia: a novel diagnostic approach inspired by first endomicroscopic 3-dimensional reconstruction

ObjectiveLoss of surface maturation and cytonuclear atypia have been regarded as the pathological ‘gold standard’ for the diagnosis of oesophageal squamous cell intraepithelial neoplasia. However, there has been no satisfactory...

Laminate system schemes for effective property estimates of architectured composites with co-(dis)continuous phases

Effective properties of fiber and laminate systems of ellipsoidal overall symmetry result from a weighted spatial average of either the effective stiffness or the effective compliance of directional fibers or laminate structures. Such systems can be considered for various (elastic, dielectric, magnetic, etc.) types of properties, including coupling. Effective properties from such fiber and laminate systems have been shown relevant for a large variety of material architectures with various phase continuity/connectivity features (Franciosi et al., 2011). For laminate systems (LS) here of concern, it has been further argued (Franciosi and El Omri, 2011) why a stiffness (resp. compliance) averaging relevantly describes two-phase assemblages with both (resp. none) through-sample continuous phases. The provided microstructural interpretations from morphological considerations resulted from a comparison of these LS schemes with the self-consistent approximation in the two-phase case. It is here shown that (i) the so established relevancy of laminate systems to represent two-phase materials with co-continuous or co-discontinuous phases does not extend to n-phase composites, (ii) for large classes of structures with any number n of co-(dis)continuous phases, referring to an equivalent two-phase material is an alternative way to establish this relevancy.

Hydrogen embrittlement of ferritic steels: Observations on deformation microstructure, nanoscale dimples and failure by nanovoiding

While hydrogen embrittlement of ferritic steels has been a subject of significant research, one of the major challenges in tackling hydrogen embrittlement is that the mechanism of embrittlement is not fully resolved. This paper reports new observations and interpretation of fracture surface features and deformation microstructures underneath the fracture surface, providing a mechanistic view of failure catalyzed by hydrogen. Linepipe grade ferritic steels were tested in air with electrochemically pre-charged hydrogen and in high-pressure H2 gas. The fracture surface features were studied and compared using high-resolution surface-sensitive scanning electron microscopy, and the deformation microstructures just beneath the fracture surfaces were studied using transmission electron microscopy. Significant dislocation plasticity was observed just beneath both ductile and quasi-brittle fracture surfaces. Further, the dislocation activity just beneath the fracture surfaces was largely comparable with those observed in samples tested without hydrogen. Evidence for hydrogen-enhanced plastic flow localization and shear softening on the sub-micron scale was observed very near the final fracture surface (<2μm) in the tensile samples. The quasi-brittle fracture surfaces were found to be covered with nanoscale dimples 5–20nm wide and 1–5nm deep. Based on analyses of conjugate fracture surfaces, most of the nanodimples appear to be “valley-on-valley” type, rather than “mound-on-valley” type, indicating nanovoid nucleation and growth in the plastically flowing medium prior to ultimate failure. Based on these observations, an alternative scenario of plasticity-generated, hydrogen-stabilized vacancy damage accumulation and nanovoid coalescence as the failure pathway for hydrogen embrittlement is proposed.

A study of changes taking place in Cu–Cr–Zr alloy during severe plastic deformation and annealing as evaluated by thermoelectric power measurements

A CuCrZr alloy has been processed by equal channel angular pressing and annealing. Changes of microstructure have been analysed using thermoelectric power measurements, which are very sensitive to the amount of solute as well as other defects introduced during processing. Severe plastic deformation of solutionized material leads to significant increases in the amount of solute, which leads to significantly more precipitation on ageing. Such factors must be taken into account in any interpretation of final microstructures and mechanical properties.

The Origin and History of the International Metallographic Society

The International Metallographic Society (IMS) is rich with history. With roots dating back to the early days of the Manhattan Project, metallographers experienced in ferrous and copper alloys were faced with a new challenge. How does one safely prepare nuclear materials (uranium, plutonium, and other materials related to the US Atomic Energy Commission (AEC) programs)? Some nuclear engineers expected metallographers to know as much about nuclear materials as they did about iron and copper alloys. The efforts of these pioneers helped to establish the basis for evaluating nuclear materials, and many of the techniques developed remain in use today. These techniques are a combination of science and art; in the early days, it took more than just a procedure to produce a desired result. It also took a developed instinct to know if a specimen was ready to come off the polishing wheel or if it needed a few more seconds for the perfect etch. Although the tasks facing them were daunting, metallographers are blessed with resourcefulness and an intense desire to solve new metallographic problems. Challenges presented by the group of nuclear materials and radioactive samples were met, and the science of metallography took a giant step forward. The methods and techniques developed for these metals and alloys have been extended to the study of nearly all present-day materials. The focus of the Manhattan Project was to develop the first atomic weapon during World War II. Metallographers supporting the Manhattan Project were employed by the AEC and its contractors. These experienced metallographers encountered textbook curiosities that dictated the need to develop new metallographic techniques. As a result, metallographers and scientists at each AEC laboratory developed their own techniques for safety control, specimen preparation, and microstructural interpretation. Each laboratory drew its own conclusions based on the microstructural interpretations. After World War II, wartime security restrictions began to ease and the AEC contractors began to hold periodic meetings. At an AEC Metallurgical Conference in January 1949, metallographers and metallurgists decided it would be useful to compare techniques for preparing and examining uranium. G. L. Kehl, Columbia University; A. U. Seybolt, Knolls Atomic Power Laboratory; and H. A. Saller, Battelle Memorial Institute-Columbus were asked to arrange an ad-hoc meeting to discuss the metallographic techniques and procedures being developed on uranium metallography. For the meeting, Battelle-Columbus agreed to fabricate and heat treat identical sets of natural uranium. These specimens were sent to other AEC-sponsored laboratories. Sixteen representatives from eight AEC laboratories met at Battelle-Columbus in July 1949 to exchange information. The success of this meeting led to further collaboration. Between 1950 and 1969, 22 AEC Metallography Group meetings were held, with attendance growing to as many as 60 in later years. By today’s standards, early meetings had exotic themes. For example, in advance of the June 1950 meeting, attendees received samples of crystal bar zirconium and zirconium-clad 6 wt.% uranium alloy. At the sixth meeting, which occurred in September 1952, attendees presented papers on the recent work of their respective laboratories and the first steering committee was elected. The Group elected Harriet Roman, MIT, as permanent S. Dekanich (&) Y-12 National Security Complex, P.O. Box 2009, Oak Ridge, TN 37831-8245, USA e-mail: dekanichsj@y12.doe.gov

Shearing of magma along a high-grade shear zone: Evolution of microstructures during the transition from magmatic to solid-state flow

Syntectonic plutons may record short-lived geological events related to crustal melting and deformation of the continental crust. Therefore, interpretation of microstructure and orientation of fabrics is critical in order to constrain space/time/temperature/deformation relationships during pluton crystallization. Here we describe the transition from magmatic to solid-state deformation in the late-Variscan Diorite-Granite Suite (DGS) emplaced along the Santa Lucia Shear Zone. The systematic collection of meso-, microstructural and quartz < c > axis data allow us to examine the spatial distribution and the mode of superposition of different fabrics. We identify three magmatic microfabric types, thought to reflect the microstructural evolution at decreasing melt content during pluton crystallization. Our data suggest that diffusion creep, dislocation creep and grain-scale fracturing cooperated in accommodating the shearing of the partially molten quartzofeldspathic aggregate. We suggest that the switch from upward to horizontal magmatic flow occurred at melt fractions gt; ∼0.40, and that most of the hypersolidus fabrics formed during horizontal flow, reflecting the stress field imposed by the shear zone, and preserving no memory of the ascent stage.

Quantitative interpretation of martensite microstructure

This work reviews issues and advances a formalism for quantitative interpretation of martensite microstructure, heeding the influence of transformation uniformity and the interaction of martensite with its surroundings. The relationship of volume fraction and number density of martensite units required for kinetics analysis is derived. Additionally we apply the new model to obtain the microstructural path function (MPF) of martensite, and to analyze the autocatalytic spread of the transformation during the martensite burst in Fe-31 wt. (%) Ni-0.02 wt. (%) C. The growth of an autocatalytic spread event relates to the chemical driving force, whereas the number of such events relates to the probability of finding a nucleation site to initiate the reaction.

Validating age in southern calamary (Sepioteuthis australis) over seasonal and life history extremes

Through rearing known age individuals and maintaining chemically marked adults in captivity, this study explored the rate of increment formation in southern calamary (Sepioteuthis australis) statoliths over seasonal (summer and winter) and ontogenetic (hatchlings and adults) extremes. A ‘one increment–one day’ relationship was verified for captive-reared hatchlings up to 40 days post-hatching which remained stable across the seasonal extremes. This relationship, however, was not evident in the chemically marked adults as inconsistencies of up to 44 days were detected between the number of days elapsed post-stain and the increment count. No seasonal effect was detected in the ratio between increment count and days elapsed, however, the degree of underestimation was consistently greater for winter-caught adults by approximately 2.5 increments relative to summer-caught adults. This less-than-daily increment formation in adults may be due to: (1) the periodicity of increment formation changing throughout the squid's lifespan; (2) deleterious effects associated with rearing squid in captivity; and/or (3) compromised interpretation of the statolith microstructure as a result of the preparation method.

Larval stage duration, age and growth of blue lanternfish Tarletonbeania crenularis (Jordan and Gilbert, 1880) derived from otolith microstructure

Tarletonbeania crenularis specimens were collected off Oregon in 2006 and 2009 and aged by enumeration of growth increments in otoliths (sagittae). Three microstructural zones were evident in the otoliths of juvenile and adult fish: central, middle, and external. The number of increments in the central zone are thought to be deposited during the larval phase which is restricted to the uppermost 350 m water layer. The middle zone constituted of barely visible increments, most likely represented a non-migratory behavior of transforming larvae and early juvenile stages. Well defined growth increments were found in the external zone which was presumably formed during extensive vertical migrations of juvenile and adult fish. If the enumerated increments were deposited daily, as previously validated for other myctophid species, the examined individuals indicated a shorter life span than has been formerly reported on the basis of length frequency analysis. The otolith microstructure interpretation was supported by otolith size to fish length proportions and somatic growth of larvae and postlarval fish. Otolith length to standard length relation was described by linear regression models for larvae and postlarval migratory stages with an abrupt disruption between these two groups. The number of growth increments in otoliths plotted against standard length showed a curvilinear growth for larvae and for the postlarval fish. The lack of information on the size at age of transforming larvae and non-migratory early juveniles did not allow us to estimate a complete growth model for T. crenularis. However, a pronounced decrease in growth between larval and postlarval migratory phases was distinguished. The uncoupling of otolith and somatic growth was interpreted as a merged effect of downward migration of larvae to the mesopelagic transformation depth, prolonged stay of transforming larvae and early juveniles at this depth without performing diel vertical migrations, and shrinkage during metamorphosis. Back-calculated hatch dates suggests a prolonged spawning season of this species without any distinct peak.

Ontogenetic change of bone microstructures and its ethological implication in Champsosaurus (Diapsida, Choristodera)

Compact cortex in a Champsosaurus (Diapsida, Choristodera) femur is ontogenetically replaced with extensively developed cancellous bone. This histological shift, together with retention of calcified cartilage to late ontogenetic stage, was previously considered to show that adult champsosaurs were more adapted to aquatic environments than juveniles. However, the new histological examination reveals the nearly amedullar condition of a juvenile femur consisting of thick periosteal cortex and less cancellous bone tissue and the amedullar but more porous condition of adult femora. This likely demonstrates that the femoral inner structure of the juvenile is denser than those of the adults, and therefore, juveniles were more aquatic. It is suggested that morphological variations between two sympatric species of Champsosaurus reflect sexual dimorphism in a single species and limb bones with more robust morphology, showing better terrestrial adaptation for nesting on land, belong to females. The similarity of gross limb bone morphology between juveniles and inferred adult males indicates aquatic habitats for juveniles, coincident with the new interpretation of bone microstructures. No differences are, however, recognised in femoral microstructure between inferred sexes in adults. The possibly lowered density of femur in adults is considered as an adaptation to increase the mobility in water.

“Introduction to Grains, Phases, and Interfaces—an Interpretation of Microstructure,” Trans. AIME, 1948, vol. 175, pp. 15–51, by C.S. Smith

“Introduction to Grains, Phases, and Interfaces—an Interpretation of Microstructure,” Trans. AIME, 1948, vol. 175, pp. 15–51, by C.S. Smith

“Introduction to Grains, Phases, and Interfaces—an Interpretation of Microstructure,” Trans. AIME, 1948, vol. 175, pp. 15–51, by C.S. Smith

“Introduction to Grains, Phases, and Interfaces—an Interpretation of Microstructure,” Trans. AIME, 1948, vol. 175, pp. 15–51, by C.S. Smith

Interpretation of X-ray diffraction analysis and TEM microstructure of MA’ed powders with peritectic reaction

Various microstructural changes take place simultaneously during the mechanical alloying process. Reduction in the crystalline size and the lattice strain cause a significant peak broadening, and dissolution of solute atoms results in peak shift in X-ray diffraction (XRD) spectrum. Therefore application of conventional XRD analysis routes is not straight forward, and could lead to incorrect information. When XRD method is used to analyze MA’ed powders, the spectrum needs to be carefully interpreted in order to extract the meaningful quantitative information. In this study, the possible sources of the error are addressed when MA’ed powders of Al–X (X = Ti, Nb) system are characterized by the XRD method, and proper XRD analysis methods are suggested to determine on lattice parameter, solubility of minor elements, crystallite size and strain variance in the MA’ed Al–X samples. The TEM observation is done to evaluate the formation of solid solution during MA.

Otolith increment width responses of juvenile Australian smelt Retropinna semoni to sudden changes in food levels: the importance of feeding history

To aid the interpretation of otolith microstructure in wild fishes, the present study assessed responses in daily otolith increment widths of early juvenile Australian smelt Retropinna semoni to sudden changes in feeding conditions. There was an almost immediate response in otolith increment widths (which can be interpreted as growth in length) to sudden changes in feeding conditions, with such changes being detected statistically after c. 4 days. Fish displayed compensatory growth when food supplies were increased following a period of limited food, indicating the magnitude of the response in growth appears highly dependant on feeding history. Additionally, fish size also appeared to influence increment widths suggesting that both fish size and feeding history are important factors that must be considered when interpreting otolith microstructure for the species.